1. Field of the Invention
The present invention relates to a moving picture encoder, a moving picture encoding method, a moving picture encoding program used therewith, and a storage medium storing the program. For example, the present invention is preferably applied to a moving picture encoder that uses the Internet to distribute moving picture data in compressed and encoded form.
2. Description of the Related Art
Recently, the distribution by the Internet of moving picture data, so-called “streaming” has come into widespread use. In streaming, by using the Internet to transmit to a user's personal computer moving picture data obtained by using a videocamera or the like to capture the picture of a subject, a moving picture based on the moving picture data is shown in real time.
In the actual distribution of moving picture data by streaming, the transfer rate at which the moving picture data can be transmitted by the Internet is relatively low. Accordingly, the moving picture data is distributed in reduced-capacity form by providing at the transmitting side a moving picture encoder employing, for example, the MPEG-2 compression encoding standard of the International Organization for Standardization/International Electrotechnical Commission (ISO/IEC), using the moving picture encoder to sequentially reduce the moving picture data in units of frame pictures by performing pixel decimation, and subsequently performing compression encoding at a relatively high compression factor.
In the above distribution of moving picture data by streaming, the resolution (level representing picture roughness) and picture quality (indicating whether noise exists) of a moving picture provided to a user deteriorate because the moving picture encoder at the transmitting side uses a relatively high compression factor to perform compression encoding. To eliminate this deterioration, enhancement of the resolution and picture quality of moving pictures for distribution is in great demand.
Accordingly, for the distribution of the moving picture data by streaming, it has been proposed that the MPEG-4 compression encoding method standard be applied to the moving picture encoder.
In MPEG-4, processing (hereinafter referred to as “simple profile processing”) for compressing and encoding moving picture data similar to that in the MPEG-2 standard can be executed by performing sequential motion-compensation interframe prediction in units of frame pictures, and processing (hereinafter referred to as “core profile processing”) is executed which tracks and extracts an arbitrary-shaped picture (hereinafter referred to as an “extracted picture”) from frame-picture-unit picture data (hereinafter referred to as “frame-picture data”) composed of consecutive picture data, and which compresses and encodes the data (hereinafter referred to as the “extracted-picture data”) of the extracted picture by performing sequential motion-compensation interframe prediction.
Accordingly, in the distribution of moving picture data by streaming, compression encoding at a relatively low compression factor is performed because, after moving picture data obtained by using a videocamera or the like to capture the picture of a subject is input to two moving picture encoders in accordance with the MPEG-4 standard, one moving picture encoder is controlled to execute simple profile processing so that the moving picture data is compression-encoded at a relatively high compression factor, and the other moving picture encoder is controlled to execute core profile processing so that the moving picture data is compression-encoded at a relatively low compression factor since the amount of extracted picture data obtained by performing sequential tracking and extraction from the frame-picture data of the moving picture data is less than that of the frame-picture data.
In addition, in the above moving picture distribution, it is possible that, by transmitting to the user's personal computer the frame-picture data and extracted-picture data compressed and encoded by the moving picture encoder, and by using the personal computer to display an extracted picture based on the extracted-picture data so as to be superimposed on a frame picture based on frame-picture data, a moving picture in which only the extracted picture is processed to have a high resolution and a high picture quality can be shown to the user.
In the above moving picture distribution by streaming, if a single moving picture encoder executes both simple profile processing and core profile processing, the transmitting side can be simplified in structure.
According to the above moving picture distribution, in a single moving picture encoder, a motion-vector detection circuit and a compression encoding circuit which sequentially compress and encode moving picture data in units of frame pictures by using simple profile processing, and another motion-vector detection circuit and another compression encoding circuit must be separately provided which sequentially track and extract picture data from frame-picture data composed of consecutive moving picture data by using core profile processing must be provided. Since the two provided motion-vector detection circuits have an extremely large processing load, the total processing load of the entire compression encoding greatly increases, so that the compression encoding requires a lot of processing time.